Chemical pulp is a man-made fiber of cellulose (C6H10O5)n, which is obtained from plant material (95% from wood) and is further processed predominantly in the paper industry, white pulp being used to produce printing and writing paper and brown pulp being used to produce paperboard and packing paper.

Chemical pulp is subdivided into the following groups:

sulfate pulp

sulfite pulp

semichemical pulp

linters

mechanical pulp (MP, TMP, CTMP)

in each case fully bleached, semibleached or unbleached.

Cellulose raw materials include all cellulose-containing materials, such as wood, cotton, straw and other annual plants. Yield varies between 15 and 80% depending on the raw material and processing method used. During production, the cellulose fibers are separated from one another, either by pressure boiling (chemical pulping) or by mechanical comminution:

CTMP is subjected initially to chemical/thermal pretreatment and is then mechanically comminuted, thereby assuming an intermediate position.

Pressure boiling is followed by multi-stage bleaching. Unbleached chemical pulp is brown.

Once dried, chemical pulp is sold commercially in sheets, pressed blocks or rolls.

A distinction is drawn between papermaking pulps and special pulps. Special pulps are individually produced for their particular field of use, the important factor generally being chemical purity.

Quality / Duration of storage

The most important features of papermaking pulps are whiteness, strength and cleanness. In paper and cardboard production, papermaking pulps are either used in the pure state or mixed with secondary fibers.

Newsprint: more or less chemical pulp or mechanical pulp depending on waste paper content

Subject to compliance with the appropriate temperature and humidity/moisture conditions, duration of storage is not a limiting factor as regards transport and storage life.

Intended use

Chemical pulps are used in the manufacture of paper and cardboard, among other things in the production of newsprint, rotogravure paper, hand-made paper, imitation parchment paper, insulating paper, kraft sack paper, kraft packing paper and toilet paper.

Countries of origin

This Table shows only a selection of the most important countries of origin and should not be thought of as exhaustive.

Chemical pulp is predominantly supplied in bales (e.g. 120 x 80 cm) weighing approx. 200 or 250 kg and rolls weighing 250 - 400 kg. According to [14], the bales may also weigh between 120 and 160 kg. Packaging generally consists of white or brown paper with a high cellulose content or of actual sheets of chemical pulp. Bales of chemical pulp are held together with wires or steel strapping. For ease of handling during loading and unloading, the individual bales are generally strapped together in units of 6 or 8 [2] or even 12 [11].

Dry pulp may be transported in standard containers, subject to compliance with limits for water content of goods, packaging and flooring. If there is too much moisture present in the container, there is a risk that condensation water may form. Where containers are not watertight, there is a risk of ingress of moisture from outside (precipitation, seawater), leading to losses. It is therefore generally better to stow the containers below deck.

Wet pulp is highly susceptible to losses in standard containers, as the high water content of the goods means that even slight temperature fluctuations may cause condensation water to form.

Cargo handling

The cargo must also be protected from moisture (rain, snow) during cargo handling (stow in hold or cover with tarpaulins in the case of truck and rail transport).

During cargo handling, ensure that surfaces are clean. In addition, forklift trucks should be checked for hydraulic fluid and oil leaks and squeeze clamps should be clean.

Papermaking pulp may also be stored in the open air in the short term, provided that it is adequately covered (tarpaulins) and the ground is clean. It is usually set down on squared lumber or pallets. Special pulp should be stored in sheds where possible.

Chemical pulp is contaminated by fibrous materials and it is therefore important, where possible, to use wire rope or chains during cargo handling.

Stowage factor

1.50 m3/t (bales in wooden frames) [1]

1.25 - 1.39 m3/t (loose bales) [11]

1.25 - 1.39 m3/t (unitized bales) [11]

1.45 - 1.56 m3/t (wet pulp) [11]

1.65 - 1.90 m3/t (bales) [14]

Stowage space requirements

Before the cargo is accepted, holds or containers must be absolutely clean (e.g. no patches of fat or oil) and dry, in particular in the case of viscose pulp (silk pulp).

In the case of transport by ship, pipework must be leak-free, bilges must be inspected and hatch covers must be watertight. Where possible, dry pulp should not be stored on deck.

Wet pulp may be transported on deck, but it must then be carefully protected from contact with seawater, to prevent blue discoloration. To minimize risks, it is therefore best to avoid stowage on deck.

Segregation

Fiber rope/thin fiber nets and marker pen/oil crayon. Do not use water-based paint, since this is absorbed by the chemical pulp and causes discoloration.

For stabilization purposes, cellulose packages may be provided with wooden frames. To prevent the packages from shifting and suffering damage during transport, the holds/containers should be tightly packed or any spaces that may remain should be filled with appropriate stowage material.

Figure 1

Figure 2

For cargo securing, see also chapter entitled Cellulose packages in the GDV Cargo Securing Manual.

The sorption isotherm for cellulose demonstrates its hygroscopicity
. During cargo handling and transport, the cargo must be protected from all forms of moisture (seawater, rain and condensation water) and excessive relative humidity. Chemical pulp has a high swelling capacity and may increase in volume by > 50% if it absorbs moisture. Its suitability for transport may then be affected, the mixture ratio with other products changes and the risk of mold attack and mustiness increases, especially at elevated temperatures. Mold spoils the pulp and causes it to disintegrate. The action of seawater causes problems, since it leads to chemical reactions as well as rust spots. Technical developments in recent years mean that processing plants react more sensitively to seawater due to closed water circuits and because most operations are carried out at neutral pH. Seawater-sodden bales may be rejected.

Wet pulp should not be stowed together with moisture-sensitive goods due to its high water content and its capacity to release water vapor.

Cargo fires should be extinguished with CO2 or foam. If a fire is extinguished with water or in the event of water ingress, the swelling capacity of chemical pulp may result in severe damage to the structure of the vessel. For example, water ingress occurred when a ship loaded with pulp was in a collision. After only a short time, the pulp bales began to swell, forcing up the hatch covers. The cargo was so saturated and swollen with water that the central area of the ship became completely deformed. Unloading proved extremely difficult, with the severely swollen bales having to be wrenched out.

Chemical pulp must be carefully ventilated, to dissipate the gases generated in production. Wet pulp should be ventilated immediately after the start of the voyage, as considerable quantities of condensation may arise due to constant water vapor release. Where wet pulp is transported in standard containers, large amounts of condensation form on the container walls. At an equilibrium moisture content of 90%, a temperature difference of just 2°C between the pulp and the container wall is sufficient to cause condensation to form on the container walls, the container ceiling being most at risk of condensation.

Chemical pulp is highly flammable, so protect from sparks, cigarette ends, fire and naked lights. Smoldering fires are also a risk. Smoking is absolutely prohibited during cargo handling. Do not stow with chemicals (acids, alkalies, gases), as explosive vapors may develop. Cargo fires should be extinguished with CO2 or foam due to the swelling capacity of the cargo.

Chemical pulp is contaminated in particular by coal, grain, fats/oils and fibrous material. Contamination by fats/oil often results in the entire cargo being lost, as the pulp becomes unfit for further processing. Do not accept any bales which are dirty or are strapped with rusty steel straps.

Chemical pulp is supplied as a finished auxiliary or end product for further processing. Contamination caused by external dirt (on the packaging) need not be considered serious as long as it is certain that the product itself is not contaminated. Internal contamination disrupts production operations. Bitumen and plastic pellets are extremely deleterious, but grain, wood splinters and other small items may also lead to production defects. The former contaminants bring with them the very real risk of consequential losses amounting to many times the value of the product (unreusable waste, machine down-time and possibly even damage to the wire and cylinder).

Chemical pulp may be attacked and destroyed by microbes and insects, especially moths. The risk of moth infestation increases if the bales are contaminated or stowed near wool bales or if their packaging consists of material susceptible to moth attack.